Notes Lipids - Notes Lipids Lipids are a group of molecules...

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Notes Lipids Lipids are a group of molecules which include: fats, oils, waxes, phospholipids, steroids (like cholesterol), sphingolipids, and prostaglandins. The main purpose of lipids is to store energy. Other very important functions include: o padding for organ o dissolving fat soluble vitamins o steroids – used in messaging, decomposition of large molecules, hormones. . o transportation of some molecules through the blood o cell membrane structure These molecules perform different functions in an organism. We will begin with fats, oils and waxes. Before we discuss lipids we should review a specific carboxylic acid, the fatty acid and esters. The functional groups for each are shown below: C O OH R C O O R R carboxylic acid ester The oxidation of a primary alcohol will lead through an aldehyde to a carboxylic acid . [O] C C H H H H H OH C C H H H H O H [O] C C H H H H O OH primary alcohol aldehyde carboxylic acid A fatty acid is simply a carboxylic acid in which the R group is very long. It consists of many carbons chained together with hydrogens completing their octet. HO C O C C H H H C H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H H H H palmitic acid - a fatty acid To create an ester an alcohol combines with a carboxylic acid in a dehydration reaction, which produces the ester and a water molecule.
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C O CH 3 O H alcohol C C H H H H H HO carboxylic acid C C H H H H H C O CH 3 O H 2 O ester Again, the main purpose of fats and oil is to store energy. Hence if you eat more calories than your body needs, you turn these extra calories into fat for storage. This is a very basic need; the more fat an organism can generate the more likely that organism will survive in times of low food supply. These days this seemingly good genetic trait has lost its usefulness. A person trying to lose weight (fat) is fighting against millions of years of evolution. They are fighting against their own genes; the genes that allowed their ancestors to survive and eventually create them. If you think about it, the battle of the bulge is really a battle against the survival of the strong. Darwin would be so upset. Or maybe not, if we look at the genes being passed down what trend will be observed over the next millennia, thinner people. People with bodies more adapted to a sedentary life. Fatty acids come in two main classes, saturated and unsaturated. These classes are have the same meaning as used in naming hydrocarbons. Saturated, like alkanes, indicates that the carbon has as many hydrogens as possible bonded to said carbons, all single bonds, no double or triple. Unsaturated, like alkenes and alkynes, indicates that hydrogens could be added to the carbon chain, for instance in an addition reaction across a double or triple bond. The palmitic acid shown above is a saturated fatty acid. Below is a picture of an unsaturated fatty acid: HO C O C C H H H C H C H H C H H C H H H H C C H H C C H H C H H C H H C H H C H H C H H C H H H
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This note was uploaded on 04/19/2010 for the course CHEMSITRY CH 106 taught by Professor Kovacich during the Spring '10 term at Portland CC.

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Notes Lipids - Notes Lipids Lipids are a group of molecules...

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